Processors of frozen cauliflower have had serious problems with discoloration of the product during normal periods and temperatures of frozen storage. To a lesser extent, problems have also occurred in softening of the texture and even the taste. These quality changes during storage of frozen cauliflower have been well known for many years. The Time-Temperature Tolerance of the Frozen Foods industry project at the Western Regional Research Laboratory of the United States Department of Agriculture, studied the discoloration and also the taste problems. The study results are reported in the October, 1962 article by W. C. Dietrich, M-D. F. Nutting, M. M. Boggs and N. E. Weinstein entitled "Time-Temperature Tolerance of Frozen Foods. XXIV. Quality Change in Cauliflower" in FOOD TECHNOLOGY 24:123-128, and also in the book entitled The Freezing Preservations of Foods, published in 1968 by AVI Publishing Company of Westport, Conn. These publications clearly establish that the rates of quality deterioration increase exponentially with rises in storage temperature within the range of 0.degree. F. to 25.degree. F. An approximate "rule of thumb" pointed out in the publications is that for each 10.degree. rise in storage temperature within the 0.degree. F. and 25.degree. F. range, the deterioration increased approximately 4-fold. The above referenced 1968 publication reports that discoloration occurs 3.6 times faster at 10.degree. F. than at 0.degree. F., and 10.7 times faster at 20.degree. F. than at 0.degree. F. The tests with industry panelists reported in the 1962 FOOD TECHNOLOGY article identified above establish that the product is not of high quality after storage from between 3 to 6 months at 10.degree. F. and after only 5 to 11 weeks at 20.degree. F. The results clearly demonstrate that color is significantly less stable than is flavor; however, perceptible flavor changes were demonstrated within 10, 2 and even 0.5 months for 0.degree. F., 10.degree. F., and 20.degree. F. storage temperatures, respectively. On the other hand, color changes were observed within even shorter storage times, to-wit: 2, 0.5 and 0.2 months at storage termperatures of 0.degree. F., 10.degree. F., and 20.degree. F., respectively. In summary cauliflower quality undergoes substantial deterioration within only relatively short periods of frozen storage and color is the least stable quality. Also, the rate of quality deterioration of the cauliflower increases very substantially with increases in storage temperature. Since specified temperatures are extremely difficult to maintain, particularly during the distribution and display of frozen food products, the problem of quality deterioration in the marketplace is very serious and has remained unsolved in the industry for over 20 years.
Consumer marketing tests also establish that the color of the cauliflower is very important to the consumer and discoloration of frozen cauliflower produces substantial consumer resistance.
A number of different chemical treatments of the cauliflower were examined primarily to determine and evaluate the effectivness for preserving the color of the frozen cauliflower under normal storage, distribution and marketing conditions. Such chemicals as citric acid, malic acid, ethylenediamine tetraacetic acid and ascorbic acid, were added to the cauliflower without appreciable beneficial effects on the preservation of the white color. The only chemical additive that has proved to be effective is sodium acid pyrophosphate (SAPP) and the minimum percentage of SAPP in the cauliflower which has proven to be effective is 0.07% by weight unless otherwise specified all per cents are by weight.
U.S. Pat. No. 4,097,612 issued June 27, 1978, which corresponds to Canadian Patent No. 999,479 and also relates generally to British Patent No. 1,510,883, are all assigned to Creston Valley Foods, Inc. of Vancouver, B.C., Canada. The U.S. and Canadian patents disclose the use of SAPP in connection with the high-temperature retort processing of potatoes (up to 250.degree. F. for approximately 1 hour for a 1-pound package), and includes the use of SAPP in the blanching operation of the 3-step retort process along with other chemicals. The British Patent No. 1,510,883 refers to other vegetables including cauliflower in addition to potatoes. The use of SAPP alone in the retort process, without the other chemicals, is ineffective to prevent discoloration of the cauliflower. It is believed that the retort cauliflower browning process involves a different chemical mechanism than is involved in the frozen storage browning process. The problem applicants have solved is the preserving of the frozen cauliflower product; frozen storage does not involve the retort process in any way.